Mobile devices, also referred to herein as Mobile Equipment (ME) can connect to many different networks. An Access Point Name (APN) is used to allow a mobile device to select and connect with a data network. The APN identifies a point of presence to which the mobile device wants to connect. Devices traditionally connect to services such as: Internet, Wireless Application Protocol (WAP), Multimedia Messaging Service (MMS), IP Multimedia Subsystem (IMS), etc. Each service usually has its own APN, however different services may also use the same APN.
An APN is an alphanumeric string that may be in the form of a Fully Qualified Domain Name (FQDN). APNs are usually stored in the mobile device and are usually provisioned by the mobile device manufacturer. Network operators are free to choose their own APN settings for a service. For example, Operator A may use APN=Internet.OperatorA for Internet service, while Operator B might use APN=dataconnect.OperatorB for Internet service. A user might also be allowed to enter an APN manually via a graphical user interface (GUI) or other man-machine interface (MMI). The point of presence the APN terminates on is a network node, such as, for example, a Gateway GPRS Support Node (GGSN) or a Packet Data Network Gateway (PGW). The point of presence is most commonly in the Home Public Land Mobile Network (HPLMN), but the point of presence could be in the Visited Public Land Mobile Network (VPLMN), if roaming.
Mobile devices can utilize a Subscriber Identity Module (SIM), Universal Subscriber Identity Module (USIM) and/or IP Multimedia Services Identity Module (ISIM) application standardized/specified in 3GPP TS 31.103 on an embedded or insertable/removable Universal Integrated Circuit Card (UICC). A UICC and a Mobile Equipment (ME) compose an instance of a User Equipment (UE).
A UICC hosts one or more applications. An example of an application found in the mobile environment is the USIM application specified in 3GPP TS 31.102. In the USIM application, there is a file or data structure defined called the APN Control List (ACL). This ACL in the USIM is standardized/specified in 3GPP TS 31.102. The ACL is used by an operator to restrict the APNs that a UE can use to set up a data connection. If the ACL is present, the ME checks to see if an APN is listed in the ACL. If the APN is found by the ME to be in the ACL, the ME can use that APN to request a data connection, otherwise in general the ME cannot.
There are also regulations in Europe that allow an ME, when roaming, to use an alternative provider than the HPLMN for Internet services. This means that the ME should be able to give the user of the device the option to enter or choose an alternative APN that allows a different provider to be used for Internet.